In manufacturing processes, such as manufacturing of (semi)conductor coatings, it is common to use processes such as sputtering or chemical vapour deposition which processes do not only produce the desired coating, but as a side effect also contaminate these coatings or surfaces with undesired substances such as carbon, hydrocarbons, or hydrocarbons comprising hydroxyl groups and the like. Manufacturing processes therefore often comprise a cleaning step for removing contaminants from a surface or coating.
Wet cleaning, using various chemicals that interact with the contaminants present on the surface, are widely used in industry. However, although wet cleaning steps have been extensively developed over the years, they often have the disadvantage that the chemicals used interact with both the contaminants as well as the semiconductor surface to be cleaned. Another disadvantage is that after the wet cleaning step, remnants of the chemicals may be present on the surface which have to be removed again as far as this is possible, rendering the cleaning process less efficient and slow.
Another disadvantage of wet cleaning is that it cannot be applied to every type of surface available. A lot of wet cleaning processes make use of aqueous surfactant solutions, acids, different types of solvents and other chemical, which are often aggressive. Sensitive surfaces, such as for example surfaces based on organic substances or oil based surfaces, are not suitable to be cleaned using a wet cleaning process.
In addition to wet cleaning processes, dry cleaning processes are use in industry such as UV cleaning, cleaning processes based on laser light, etc. Each of the cleaning processes have their own field of application, and comprises its own disadvantages.
In recent years, the use of plasmas as a dry cleaning process has been proposed in certain fields of application. Plasmas are also used for all kinds of surface modification techniques. A specific application of plasmas, for example, is to improve the adhesive properties of some surfaces. A disadvantage of using plasmas for this purpose is that the stability of plasmas is often insufficient leading to uncontrollable phenomena such as streamer formation. Due to these effects, plasma cleaning may locally on a surface lead to effective cleaning, but locally on other parts of the surface it leads either to no cleaning at all or to the surface properties of the surface being modified as well. This limits the field of application of plasma cleaning processes extensively.